The present invention relates to a temperature-protected semiconductor circuit configuration having an integrated switching unit. The integrated switching unit has a semiconductor switch and a first integrated temperature sensor connected to and driving the semiconductor switch if an over-temperature condition is detected. A first connecting terminal is connected to the semiconductor switch and is to be connected to a load. A second connecting terminal is connected to the semiconductor switch, and a control terminal is provided for applying a drive signal to the semiconductor switch.
Integrated switching units containing a semiconductor switch and an integrated temperature sensor for actuating the semiconductor switch in the case of overtemperature are, for example, integrated power semiconductor switches that are sold by the Infineon Technologies AG by the names of HITFET or PROFET.
A temperature sensor monolithically integrated in the same chip as the semiconductor switch detects the temperature directly in the chip in the switching units and thus provides for fast, virtually undelayed turning-off of the semiconductor switch before a high temperature is reached which permanently damages the switching unit. In the PROFET, a status signal is also output which indicates the switching state of the semiconductor switch.
In some of the known switching units, for example the HITFET, the semiconductor switch turns off due to the temperature, and no corresponding status signal is passed to the outside. When a number of such interconnected switching units are used in an application such as, for example, a bridge circuit for driving a motor, the early recognition of a temperature-related turnoff of a semiconductor switch in a switching unit makes sense so that, if necessary, the other switching units can be suitably actuated even before the temperature limit for an automatic turn-off is reached.
Providing a capability for outputting a status signal in the case of a temperature-related turn-off of the semiconductor switch would require a new configuration of the entire switching unit. The detection of the switching state from the outside for generating a status signal is currently performed by voltage detection at the load terminals of the switching unit or by a shunt connected in series with the load terminals.
In power switches of the PROFET family, a status signal is generated and delivered to the outside, which indicates the automatic turn-off of the semiconductor switch. In these power switches, a turn-off can be due both to an over-temperature in the chip and to a short circuit in the load to be switched, which is detected by an evaluation of the voltage across the semiconductor switch. The status signal does not allow any distinction with respect to the fault that has occurred. In the case of an automatic turn-off of the semiconductor switch due to the integrated temperature sensor, the semiconductor switch also turns on again automatically when the component has cooled down, and the status signal also changes its state. The status signal thus changes its state with the heating and subsequent cooling cycle of the switching unit, which makes it more difficult to evaluate it.
It is accordingly an object of the invention to provide a temperature-protected semiconductor circuit configuration that overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which a switching unit with an integrated temperature sensor is used and in which an over-temperature in the switching unit can be detected from the outside.
With the foregoing and other objects in view there is provided, in accordance with the invention, a temperature-protected semiconductor circuit configuration containing an integrated switching unit. The integrated switching unit has a semiconductor switch, a first integrated temperature sensor connected to and driving the semiconductor switch if an over-temperature condition is detected, a first connecting terminal connected to the semiconductor switch and to be connected to a load, a second connecting terminal connected to the semiconductor switch, and a control terminal for applying a drive signal to the semiconductor switch. A second temperature sensor is connected in a heat-conducting manner to the integrated switching unit and has at least one output terminal outputting a temperature-dependent temperature signal.
Accordingly, the semiconductor circuit configuration has a switching unit with an integrated first temperature sensor and a second temperature sensor, the second temperature sensor being connected to the switching unit in a heat-conducting manner. For this purpose, the second temperature sensor is preferably mounted directly on the chip of the switching unit. To produce a thermally conductive connection between the temperature sensor and the chip of the switching unit, the temperature sensor is attached to the chip of the switching unit, for example by a thermally conductive adhesive, or by screws, clamps or the like. The first monolithically integrated temperature sensor, which detects the temperature directly in the semiconductor body of the integrated switching unit, provides for a fast turn-off of the semiconductor switch in the case of an over-temperature condition. The second temperature sensor detects the temperature on the surface of the semiconductor body and is used for providing a temperature signal that reproduces the temperature conditions in the switching unit. Because heat propagation takes time, the second temperature sensor responds more slowly than the integrated first temperature sensor. However, a time delay in providing the temperature signal is acceptable since, when the temperature signal indicating an over-temperature is generated, the semiconductor switch is usually already turned off so that there is no risk of damage to the semiconductor switch.
In accordance with an added feature of the invention, a drive circuit is connected to the control terminal of the integrated switching unit and to the output terminal of the second temperature sensor.
In accordance with an additional feature of the invention, the second temperature sensor is mounted directly on the switching unit.
In accordance with another feature of the invention, the second temperature sensor is bonded to the integrated switching unit in a dielectrically insulated manner and by a thermally conductive adhesive.
In accordance with a further feature of the invention, screws are used for attaching the second temperature sensor to the integrated switching unit.
In accordance with a concomitant feature of the invention, clamps are used for attaching the second temperature sensor to the integrated switching unit.
Furthermore, it is recognized that the switching unit can be a conventionally or commercially available switching unit having the integrated temperature sensor.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a temperature-protected semiconductor circuit configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.